Reclus (named after Élisée Reclus; sometimes confused with Cerro Mano del Diablo southwest of Reclus), also written as Reclús, is a volcano located in the Southern Patagonian Ice Field, Chile. Part of the Austral Volcanic Zone of the Andes, its summit rises above sea level and is capped by a crater about wide. Close to the volcano lies the Amalia Glacier, which is actively eroding Reclus.
The volcano has been active during the late Pleistocene and Holocene. A large eruption – among the largest known in the Austral Volcanic Zone – occurred 15,260–14,373 years before present and released over of tephra. This tephra fell out over a large area of Patagonia as far as Tierra del Fuego, and disrupted the ecosystem in the region. Subsequently, further but smaller eruptions occurred during the Pleistocene and Holocene. The last historical eruption was in 1908.
The volcano is remote and monitoring began only recently. Two dams are located close to the volcano and might be impacted by future eruptions.
Geography and geology
Regional
South of the Chile Triple Junction, the Antarctic Plate subducts beneath the South American Plate at a rate of . This subduction process is responsible for volcanic activity in the Austral Volcanic Zone; south of the southernmost volcano of this zone, Fueguino, the subduction gives way to strike-slip faulting. This subduction process is not accompanied by much earthquake activity.
Not all volcanism at these latitudes was triggered by subduction; during the Miocene the Chile Rise was subducted here and this caused a temporary pause of the subduction process and the formation of a slab window. During this period, southern Patagonia was subject to extensive basaltic volcanism. Later subduction restarted and the Austral Volcanic Zone was born.
Farther north in Chile and Argentina, volcanism occurs as a consequence of the subduction of the Nazca Plate beneath the South America Plate, forming the Central Volcanic Zone in northern Chile and Argentina and the Southern Volcanic Zone in southern Chile and Argentina. These two volcanic zones are separated from each other and the Austral Volcanic Zone by gaps without recent volcanic activity.
Local
Reclus is a high pyroclastic cone, featuring a wide summit crater and is a small volcano. Seen from above, the volcano has the shape of an egg; the pointy end points due west and consists of thick remnants of dacitic rocks of pre- or inter-glacial age. The rest of the volcano consists of a wide outcrop of violet-reddish-brown pyroclastic material that is in part covered by snow. Traces of glacial erosion are not widespread on the edifice, but a radial pattern of erosional gullys overlays the volcano. In 2019, a landslide took place on its northeastern flank, which propagated below the Amalia Glacier. Lava and pyroclastics are its principal output.
The volcano rises within the cirque of the Amalia Glacier and the glacier is actively eroding Reclus; retreat of the glacier in the 1980s has exposed part of the volcano. Reclus lies about east of the Amalia Fjord. The Southern Patagonian Ice Field and the Cordillera Sarmiento are found in the neighbourhood of Reclus, and Torres del Paine is east of the volcano. Politically, the volcano lies in the commune of Natales.
The volcano was at first confused with Cerro Mano del Diablo, a mountain located southwest of Reclus proper and formed by sedimentary rocks; only in 1987 was the volcano's true location discovered. This volcano, like other volcanoes of the Austral Volcanic Zone, is not monitored and lies at considerable distance from human habitation. This remoteness of the volcanoes in the region and the frequently hostile weather conditions often make it difficult to identify volcanoes and their precise location.
Reclus is part of the Austral Volcanic Zone, a belt of volcanoes at the southernmost tip of South America which includes six volcanoes: from north to south, Lautaro, Viedma, Aguilera, Reclus, Monte Burney and Fueguino. These volcanoes are not very high, seldom exceeding . With the exception of the last they are all stratovolcanoes with glaciers and evidence of Holocene activity; Lautaro erupted in 1959. Activity in the Austral Volcanic Zone has resulted in the widespread deposition of tephra in southernmost South America. All of them have erupted exclusively andesite or dacite; basalts or basaltic andesite are absent in contrast to the Southern Volcanic Zone farther north. These rocks in the case of the Austral Volcanic Zone are all of adakitic character, but there does not appear to be an unifying reason for this chemistry among the various volcanoes.